Level transmitters

Level measurement of any type of liquid and paste-like media with level transmitters

Stainless steel probe for continuous level measurement in water or waste water applications. Flush mounted ceramic sensor. Pressure range 0.4 bar to 25 bar.

Probe LMK 382

Stainless steel probe for continuous level measurement in waste water, waste and higher viscosity media. Pressure range 0.04 bar to 20 bar.

Probe LMP 307

Stainless steel probe for continuous level measurement in water and clean or waste fluids. Pressure range 0.1 bar to 25 bar.

Screw-in transmitter LMK 331

Screw-in transmitter for level and process measurement of liquids, oils and gases. Pressure range 0.4 bar to 60 bar.

Screw-in transmitter LMK 351

Screw-in transmitter for measuring small system pressure and level in containers.Ceramic sensor. Pressure range 0.04 bar to 20 bar.

Level transmitters

Level transmitters for hydrostatic level measurement

Level transmitters are a special type of pressure sensor used for measuring levels in containers, shafts, tanks, basins or wells. The level or the filling height of the liquid in the container is measured hydrostatically. The hydrostatic measuring principle is based on the effect of the weight force or liquid column rising proportionally to the filling level and acting on a surface. In the case of level sensors, this force acts on the sensor which converts the force into an analogue signal. This measuring principle is ideally suited for all types of flow-free, liquid and pasty media.

Hydrostatic level measurement – principle and technology

Hydrostatic level sensors operate on a simple physical principle: the pressure at the base of a liquid column increases in proportion to the height of the liquid. The formula is p = ρ × g × h, where ρ is the density of the medium, g is the acceleration due to gravity and h is the height of the liquid column. In practice, this means that one metre of water column generates around 100 mbar of hydrostatic pressure. The level sensor at the bottom of the tank measures this pressure and converts it into a standardised 4–20 mA signal. This allows the level to be monitored in real time without the sensor having any moving parts. TRI-MATIC supplies level sensors made of stainless steel or plastic for water, wastewater, oils and chemically aggressive media, featuring ceramic or stainless steel measuring cells and an IP rating of up to IP68. The range is complemented by explosion-proof (ATEX, IECEx) variants and versions with SIL 2 (functional safety) for safety-critical applications.

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Hydrostatic level measurement – the right probe for every application

Immersion probes or level probes provide precise measured values in open containers.

Immersion probes or level probes are mainly used in open containers, shafts or basins. The probe is lowered and fixed at the lowest point in the container and measures the pressure of the liquid column above it. The level is calculated from the measured pressure and the product density.

Screw-in probes for closed, pressurised systems

The screw-in probe is particularly suitable for closed vessels or systems that are under pressure. The probe is screwed in at the lowest point in the vessel. There, the screw-in probe detects the prevailing hydrostatic pressure which gives a direct indication of the current level and the height of the liquid column above it.

For aggressive media and explosion-proof environments

Touch and screw-in probes are available in many different designs. The combination of different sensor technologies such as ceramic and stainless steel housings, cables and sealing materials enables use with aggressive media or in explosion-proof environments.

The application areas of hydrostatic level measurement are extremely diverse: from drinking water or wastewater management, to the chemical or paint industry, all the way to the food industry.

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FAQ

How does hydrostatic level measurement work?

Hydrostatic level measurement is based on the relationship between liquid height and pressure: p = ρ × g × h. A sensor mounted on the bottom of the tank measures the pressure generated by the column of liquid above it. As the pressure increases linearly with the level, the level can be reliably calculated. The method is suitable for all liquids and paste-like media with a known density.

Which level sensor is suitable for water and wastewater?

For level measurement in water and wastewater, TRI-MATIC recommends immersion probes made of stainless steel or plastic with a ceramic measuring cell. The LMK 307 is designed for clean to slightly contaminated water, whilst the LMK 382 has been specifically developed for wastewater and contaminated media. Both models offer IP68 protection and are suitable for continuous use underwater.

What is the difference between an immersion probe and a screw-in probe?

The choice depends on the application:

Immersion probes (e.g. LMK 307, LMK 382) are immersed directly into open tanks, wells or channels. Ventilation is provided via a capillary tube in the cable.
Screw-in probes (e.g. LMK 331, LMK 351) are screwed into the side or bottom of closed, pressurised tanks. In addition to the level, they also measure the overpressure.

Both variants are available as pressure sensors with a ceramic measuring cell.

How accurate are hydrostatic level sensors?

Accuracy depends on the measuring range and the measuring cell. TRI-MATIC level sensors typically achieve an accuracy of ≤ 0.35 % of the span. For applications requiring greater precision, models with a piezoresistive stainless steel measuring cell offer accuracies from 0.1 %. Correct zero-point calibration when the tank is empty, as well as a known and, as far as possible, constant medium density, are also crucial for measurement quality. Further information on measurement principles can be found on our page on pressure sensors and pressure transducers.